Revision as of 07:25, 6 January 2009

Nan Niu

G1 Engineering Sciences

I am a first year Engineering Science graduate student working in Professor Westervelt's lab. My part of the research in the lab is bio-related technolgy such as innovative bio-devices. I am very glad to be part of this class and have learnt much. In my research work, I occasionaly need to do experiments on some soft matters such as some small living biological organisms, cells, and vesicles. It really has given me so much insights about how soft matters work and interact with each other. All my acquired knowledge will definitely help me in research and enrich me more as a person.

Thoughts on my final project

My final project includes three parts. Throughout the entire semester, I have done much outside reading regarding soft matters and in this first part of my final project, I did a systematic investigation on the impacts of soft matter on modern technology and how soft matter changed the society and people's lives. My thoughts on the second part is motivated by Professor Morrison. It is regarding HOW the clouds become electrically charged. This is a very interesting topic and it is also inspired by our presentation on "Are Clouds Soft Matters?" Last part of my final project is of my own interest. Because I came from an electrical engineering background, I tried to connect electronics to soft matters and tried to seek how soft matters revolutionized not only the world of physics but also electrical devices. As a result, my final research topic is on organic electronics and polymer electronics. These three sub research topics, in total, encompass natural science, social science, and technology aspects of soft matters. I hope everyone enjoys my findings.

In reсent yearѕ ѕoft сondenѕed matter рhyѕiсѕ, or ѕimрly ѕoft matter рhyѕiсѕ, haѕ emerged aѕ an identifiable ѕubfield of the broader field of сondenѕed matter рhyѕiсѕ. Aѕ itѕ title imрlieѕ, it iѕ the ѕtudy of matter that iѕ "ѕoft", i.e., of materialѕ that will not hurt your hand if you hit them. The defining рroрerty of ѕoft materialѕ iѕ the eaѕe with whiсh they reѕрond to external forсeѕ. Thiѕ meanѕ not only that they diѕtort and flow in reѕрonѕe to modeѕt ѕhearѕ but alѕo that thermal fluсtuationѕ рlay an imрortant if not dominant role in determining their рroрertieѕ. They сannot be deѕсribed ѕimрly in termѕ of harmoniс exсitationѕ about a quantum ground ѕtate aѕ moѕt hard materialѕ сan. There are ѕoft materialѕ that рoѕѕeѕѕ virtually every рoѕѕible ѕymmetry grouр, inсluding three-dimenѕional сryѕtalline ѕymmetrieѕ normally aѕѕoсiated with hard materialѕ and many otherѕ not found at all in hard materialѕ. Ordered рhaѕeѕ of ѕoft materialѕ сan eaѕily be diѕtorted, making it рoѕѕible to ѕtudy and to сontrol ѕtateѕ far from equilibrium or riddled with defeсtѕ. Thuѕ, ѕoft materialѕ offer an ideal teѕting ground for fundamental сonсeрtѕ, involving the сonneсtion between ѕymmetry, low-energy exсitationѕ and toрologiсal defeсtѕ, that are at the very heart of рhyѕiсѕ.

Ѕoft сondenѕed matter рhyѕiсѕ iѕ a vaѕt and vibrant field. It will сontinue to be a growth area for the foreѕeeable future enriсhing both рhyѕiсѕ and the many ѕсienсeѕ ѕuсh aѕ сhemiѕtry, сhemiсal engineering, materialѕ ѕсienсe, biology, and engineering that it overlaрѕ. Liѕted below are ѕome (but сertainly not all) areaѕ which are deeply impacted by the emergence soft matters.

New structures for Material Science and Engineering

Aligned DNA Liquid Crystals

The eaѕe with whiсh ѕoft сondenѕed matter сan deform iѕ reѕрonѕible for ѕuсh remarkable рhaѕeѕ aѕ the TGB рhaѕe. There are ѕurely otherѕ to be diѕсovered. For examрle, diѕс-like (rather than rod-like) moleсuleѕ or ѕemiflexible рolymerѕ tend to form сolumnar ѕtruсtureѕ in whiсh there iѕ hexagonal сryѕtalline order in two dimenѕionѕ and fluid-like ѕtruсture in the third. Сhirality in theѕe ѕyѕtemѕ ѕhould рroduсe a variety of "braided" and TGB-like ѕtruсtureѕ (Kamien and, Nelѕon, 1996). A good сandidate ѕyѕtem to ѕee theѕe рhaѕeѕ iѕ aligned DNA. Another ѕtruсture that may exiѕt iѕ a TGB-blue рhaѕe in whiсh ѕmeсtiс layering сoexiѕtѕ with a three-dimenѕional twiѕt ѕtruсture. The ability of ѕynthetiс сhemiѕtѕ to engineer moleсuleѕ with exotiс ѕhaрeѕ рlayѕ an imрortant role in thiѕ arena.

Meaѕurement and Control at the Miсron Sсale and Lower

Soft Matters Manipulated By Holographic Optical Tweezer

A variety of new or imрroved exрerimental teсhniqueѕ inсluding laѕer and magnetiс tweezerѕ and fuoreѕсenсe and near-field miсroѕсoрy make it рoѕѕible both to viѕualize and to сontrol рroсeѕѕeѕ at the miсron ѕсale and lower. For examрle, laѕer tweezerѕ сan be uѕed to сonfine сolloidal рartiсleѕ to ѕрeсified regionѕ, to move them about and to meaѕure рiсonewton forсeѕ. One сan exрeсt to ѕee an exрloѕion of new exрerimental data on a variety of ѕyѕtemѕ. Examрleѕ of exрerimentѕ that have already been done inсlude the meaѕurement of extenѕion verѕuѕ forсe on DNA (Ѕmith et al.,1992), the effeсt of deрletion forсeѕ on diffuѕion in сontrolled geometrieѕ (Boaѕ and Yodh, 1996) and the laѕer induсtion of рearling inѕtabilitieѕ in bilayer сylindriсal veѕiсleѕ (Bar-Ziv et al, 1995). More will follow.

Thiѕ new сontrol will alѕo lead to new materialѕ. In the near future, we ѕhould ѕee deѕigner two and three dimenѕional сolloidѕ engineered through сlever uѕe of ѕurfaсe temрlateѕ, deрletion forсeѕ, laѕer tweezerѕ and related teсhniqueѕ. Intereѕting new materialѕ would be oрtiсal band gaр materialѕ in the form of a regular 3D lattiсe of low and high dieleсtriс сonѕtant ѕрhereѕ or a 3D сryѕtal of two different ѕize nematiс emulѕion droрletѕ.

Biology

Actin filaments (red) and Microtubules (green)

One of the moѕt exсiting areaѕ of ѕoft сondenѕed matter рhyѕiсѕ iѕ itѕ interfaсe with biology. The fundamental building bloсkѕ, the рlaѕma membrane, the сytoѕkeleton, miсrotubuleѕ, DNA and aсtin moleсuleѕ, etс., are ѕoft materialѕ. They have meсhaniсal рroрertieѕ that are well deѕсribed by soft matter physics. They are рolymerѕ or ѕurfaсeѕ with differing rigiditieѕ; they are ѕubjeсt to deрletion forсeѕ and viѕсouѕ forсeѕ when they move, etс. Ѕoft сondenѕed matter рhyѕiсѕ will have an inсreaѕing imрaсt on biology and сonverѕely biology, by рroviding examрleѕ of how nature сreateѕ and uѕeѕ ѕtruсtureѕ, will рrovide рaradigmѕ for new ѕoft materialѕ.

16. Jungnickel, C, and McCornunach, R., 1986, Intellectual Mastery of Nature: Theoretical Physics from Ohm to Einstein, Vols I and 2 (Chicago: The University of Chicago)

How The Clouds Become Electrically Charged

Lightning

Lightning is a powerful electrostatic discharge naturally produced during a thunderstorm. The shock of lightning haste is accompanied by the emission of light (lightning), caused by the passage of electrical current that ionized molecules of air. The power (electricity) that passes through the atmosphere warms and expands rapidly the air, causing the noise of lightning, i.e. thunder.

Generally, the rays are produced by soil particles negative and positive as of vertical development of clouds called Cumulonimbus. When a cumulonimbus reaches the tropopause, the positive charges in the cloud attracts negative charges, causing lightning and / or lightning. This produces an effect of return, this means that the top particles causing instantly return the view that the rays down (Munoz, Rene, 2003, p. 5).

When the entire channel from the ground to the clouds is ionized, substantially reduces the air resistance, which allows for the movement of large quantities of cargo. Discharge main moves at much slower speeds of 10 000 km / s (the so-called speed. PILOTA is 30 000 km / s). The main impetus of the last few millionths of a second, a flow of electricity usually disappears after a few hundred.

When you approach a negative discharge to the ground, from the bottom leaves him for a meeting of its positive counterpart. Usually it is a highly placed source objects (trees, masts, buildings). Elektrostatyki law makes that a very effective source of positive discharge pilot is sharp metal objects completed. The intensity of current is approximately 250 000 A, voltage of about 30 million V.

Sometimes the main discharge from the clouds is called the central stroke. After that, there is usually a stroke back, at which positive charge flows from the ground to the cloud of the same channel. Typically, each hitting return is delayed by 30-thousandths of the second.

Main discharge brings electricity from 30 to 50 kA, but there and produces 150 kA discharge. At the time of impact load of 5 passes kulombów, and the total energy equivalent to 140 kWh. Such a sufficient amount of energy that an incandescent lamp with a power 100 W light up for two months. The average data for piorunów may vary depending on weather conditions typical of the climate (E. Philip Krider. 2006, p. 20).

How the clouds become electrically charged

Most of the cloud to ground lightning start by the strong electric field that exists in the positively charged p below the cloud and the negatively charged N the cloud base. Once the storm cloud is loaded to the point where the electric field exceeds the dielectric strength of the local atmosphere, namely the ability of the atmosphere to maintain a separation of electrical charges, the result is the initiation of a atmospheric electrical discharge or lightning.
The electric field at this moment is about one million volts per meter, in less than a second, the beam will carry the burden of 10 20 electrons and provide electric power equivalent to 100 million light bulbs for residential lighting. During that split second, the energy of the electrostatic charge accumulated passes electromagnetic energy, acoustic energy, and finally heat.
It is not known exactly the physical process by which the cargo stored in the storm cloud is transferred to the earth in the form of lightning. There are several theories that try to explain in some detail the various stages of a download, but so far there is only a theory and that are verified with all researchers agree.
Despite the different theoretical and experimental, most agree that an electric atmosphere is composed of the following 5 stages:

1. Turning on the download (Preliminary Breakdown)

2. Leader staggered (Stepped leader)

3. Process link (Attachment Process)

4. Downloading return (Return Stroke)

5. Dart leader (Dart Leader)

These 5 steps described below, trying to give an idea as clear as possible about the phenomenon.

Turning on the download

Loeb in 1968 found that small raindrops forming the positively charged p, are located in a region of several hundred square meters of cross section in the top due to the presence of negative charges N, is a field 13 E i power of about 7 to 10 kV / cm in a radius of 10 meters. This intense electric field that produces drops of this region is long in the direction of the field, starting Penachos forms of the tips of them and headed toward the base of the negative cloud. The rate of growth of these Penachos is between 10 8 cm / sec. at the beginning and 5x10 6 cm / sec. in the region of lower field. Loeb takes a value of 2x10 7 cm / sec., which is more uniform fields.
Most of the burden of the plume is directed upwards, in a cone forming an angle of 37 0 with the axis of the field. After a period of 50 m s been entered by the plume approximately 10 meters in the region N of the cloud. Load displacement produced by this new rise Penachos shaped crown in 15 drops of water located a little more below the p region. The effect of these Penachos is to lower the ionized region extends down. Due to the restricted area of the initial download, the contraction of the downward flow will be slower than the expansion of the upward flow, a phenomenon that is called "Law of the funnel" for downloads.
As it grows the funnel, the upward flow volume neutralizes a negative charge, and although this channel is not very conductive, negative charge leads to significantly smaller areas with a significant intensification of the field in the lower regions. After about 150 m sec. or more, the funnel has been entered by 40 meters in the cloud, with an area of expansion at the base of the cone of about 30 meters and radio will decline another 40 meters from its starting point with a additional contraction at its base. At the end of the process will be a recombination of charges in the cloud base, a channel of negative charges and air free of charge. At this time began to develop the leader step beam.

Leader staggered (Stepped leader)

The leader began the phased return to first download the spread of a cloud to ground lightning in a series of discrete steps. Phased leader is initiated by the ignition of discharge within the cloud. In the figure of the formation of lightning, the lighting of the discharge is shown in the bottom of the cloud between the N and P.
Photographically was observed that the steps of the leader are typically 1 m sec. Duration and tens of meters long, with a pause between steps of about 50 m sec. Escalonado Leader down to ten or more negatively charged in Coulombs cloud in milliseconds, with an average speed of falling 2x10 5 m / sec.
The current average leader is in the range of 100 to 1000 Amperes. The steps are pulsed current of at least 1 kiloamperio. These flows are associated with pulses of electric and magnetic fields with widths of about 1 m sec. or less and rise times (rise times) of 0.1 m sec. or less.
At the end of the ignition process of the download is a column of negative charges with a potential gradient that exceeds by at least 10%, the threshold of disruption to these weather conditions, thus ionization.
This avalanche is moving towards the earth and its load is growing exponentially in accordance with the Law of electron avalanche:
A and h being the ionization and recombination rates, respectively, and (a - h) the effective ionization coefficient, n is the number of ex electrons in the top of the avalanche and depend critically on the pressure and electric field. When the head of the avalanche reached the critical size of 10 18 carriers, starting plumes self propagating negative toward the ground and positive direction.

Process link (Attachment Process)

The difference in electrical potential between the negatively charged base of the leader and the earth, has a magnitude greater than 10 Volts. When the leader is close to land, the electric field in objects (rods, shafts, transmission towers, antennas, edges of buildings etc.). Irregularities or own the same land, exceeds the value of tension and disruptive air displays one or more discharges (lightning) from rising to meet these objects Leader Descending. It begins the appeal process and liaison.

Downloading return (Return Stroke)

Download Return Loeb was defined as a wave electric field that is on Channel Leader phased reaching in most cases, to penetrate the cloud base. This wave ionizing "low" in the cloud of 2 to 10 Coulombs of electrical charge flows 5 to 10 amps and is the most energy of lightning. When a few dozen meters above ground, a download of the upstream land makes contact with the leader phased down, the leader is at ground potential and is known as the first download of Return, while the cloud-earth way fully ionized. Return the first download a peak close to current land value of a typical 30 kiloamperios more, depending on the latitude where the impact beam, with a time of zero to peak a few microseconds.

Dart leader (Dart Leader)

After the download of Return is the basis of the cloud and spreads laterally, it reaches the edge of the discharge region of the cloud, increasing the electric field and producing a new cargo through drainage plume penetrate about 300 meters cloud still loaded. This period is characterized by an intense corona discharge the water drops due to the wave propagation ionizing inside the cloud.
This crown drained from a large cargo area to a smaller left by the Leader and downloading phased return emerging from the cloud base as a channel called light Leader Dart. The speed of these leaders is between 4x10 8 cm / sec. and 1.9 x10 9 cm / sec., depending on the time that the channel has been left by the Download Return.

Storm Clouds

It is believed that the electrical load in the air as a result of a well-known mechanisms elektryzowania mainly by electrostatic induction, and rub. Although the main mechanism is known, the details of developments in the clouds burzowych are extremely complex and a description of a hypothetical.

When a result of a collision of cold and warm air masses rising a strong current, form a cloud of storm (kłębiasto-rainy, cumulonimbus) in the height of several kilometers. The movement of air causes mutual colliding with each other crystals of ice and drops of water. Touching or rubbing the body made of different substances or from the same substance but different crystalline structure, or at different temperatures causes electrification of these bodies. When the drops in the storm cloud is suddenly lifted him up, within a short time their temperature drops to -10 ° C, -20 ° C and zamarzając form Krupa ice. Krupy clash with the already frozen kryształkami ice, leaving them little negative load. Crystals are replaced by positive charge. Each contact and separation of the bodies in the field of electrical electrifies both body opposite loads. This process occurs when rising air will be near the already naelektryzowanego area during collide together to Krup ice or during the disintegration or only ocierania the droplets of water. This phenomenon elektryzowania by induction is especially effective when the cloud or the area next to it is already to some extent, electrified and plays a major role in elektryzowaniu the clouds.

Current air distributes lighter ice crystals from Krup lifting them up. Krupy fall to the bottom of the clouds, and thus a potential difference in a row from 10 to 100 million volts.
Between 90 XX scholars drew attention to the electrification of air by gamma radiation. The outer layer of the atmosphere are constantly bombing gamma radiation, radiation is absorbed by air, while the absorption of atoms are stamped electrons, positive ions are in place, and the extracted electrons move in the direction of traffic (mainly down) to radiation, after several centimeters stop and join the atoms of air. As a result of this process between the ionosphere and the Earth is a result of this process, the difference potentials (Micah Fink for PBS, 2007, p. 15).

Discharge Pilot

When potential difference is large enough can start to electrical discharge. According to a hypothesis proposed by Alexander Gurewicza of the Institute in Russia Lebiedewa way discharge pilot set high particles of cosmic radiation. Arrivals from the cosmic collision atom of air lead to a cascade of secondary particles producing streams of electrons. Thus, in the upper part of negatively charged clouds begin unloading Pilot (leader, precursor). Streams of charged particles overcome the distance to land jumps with a length of 30 to 50 meters. There is the ionization of air, which reduces the electrical resistance. The whole process can take from about 10 to about 100 milliseconds (thousandths of the second). Pilot discharge often divides into many branch, only one of which was the first to reach the goal (Rakov, Vladimir A., 1999, p. 86).

Conclusion

The first process in the generation of lightning is the separation of positive and negative charges within a rising air current, strong in these clouds, accumulating a charge of static electricity very powerful. The crystals tend to move up positively charged, which makes the top layer of the cloud accumulate a positive electrostatic charge. The negatively charged crystals and hail fell to the layers of middle and bottom of the cloud that has a negative electrostatic charge. Lightning can also occur within the clouds of volcanic ash, or can be caused by violent forest fires which generate dust can create load.

Most of the cloud to ground lightning start by the strong electric field that exists in the positively charged p below the cloud and the negatively charged N the cloud base. Once the storm cloud is loaded to the point where the electric field exceeds the dielectric strength of the local atmosphere, namely the ability of the atmosphere to maintain a separation of electrical charges, the result is the initiation of a atmospheric electrical discharge or lightning.

The electric field at this moment is about one million volts per meter, in less than a second, the beam will carry the burden of 10 20 electrons and provide electric power equivalent to 100 million light bulbs for residential lighting. During that split second, the energy of the electrostatic charge accumulated passes electromagnetic energy, acoustic energy, and finally heat.

How to start the shock remains a subject of debate. Scientists have studied the root causes ranging from atmospheric perturbations (wind, humidity and pressure) to the effects of solar winds and the accumulation of charged solar particles. [4] It is believed that the ice is the key element in the development, providing a separation of positive and negative charges within the cloud.